Misplaced Pages

#164835

113-452: LOIC performs a DoS attack (or, when used by multiple individuals, a DDoS attack ) on a target site by flooding the server with TCP , UDP , or HTTP packets with the intention of disrupting the service of a particular host. People have used LOIC to join voluntary botnets . The software inspired the creation of an independent JavaScript version called JS LOIC , as well as LOIC-derived web version called Low Orbit Web Cannon . These enable

226-465: A Content-Length field to specify the size of the message body to follow. However, the attacker then proceeds to send the actual message body at an extremely slow rate (e.g. 1 byte/110 seconds). Due to the entire message being correct and complete, the target server will attempt to obey the Content-Length field in the header, and wait for the entire body of the message to be transmitted, which can take

339-519: A botnet of thousands of devices, the attackers can generate sufficient packet rates and occupy bandwidth to saturate links, causing the denial of services. Because of this weakness, the network company Cloudflare has described SSDP as the "Stupidly Simple DDoS Protocol". Web server A web server is computer software and underlying hardware that accepts requests via HTTP (the network protocol created to distribute web content ) or its secure variant HTTPS . A user agent, commonly

452-443: A terabit per second . Some common examples of DDoS attacks are UDP flooding , SYN flooding and DNS amplification . A yo-yo attack is a specific type of DoS/DDoS aimed at cloud-hosted applications which use autoscaling . The attacker generates a flood of traffic until a cloud-hosted service scales outwards to handle the increase of traffic, then halts the attack, leaving the victim with over-provisioned resources. When

565-422: A web browser or web crawler , initiates communication by making a request for a web page or other resource using HTTP, and the server responds with the content of that resource or an error message . A web server can also accept and store resources sent from the user agent if configured to do so. The hardware used to run a web server can vary according to the volume of requests that it needs to handle. At

678-474: A DDoS, attacks may involve forging of IP sender addresses ( IP address spoofing ) further complicating identifying and defeating the attack. These attacker advantages cause challenges for defense mechanisms. For example, merely purchasing more incoming bandwidth than the current volume of the attack might not help, because the attacker might be able to simply add more attack machines. The scale of DDoS attacks has continued to rise over recent years, by 2016 exceeding

791-647: A DNS name lookup request to one or more public DNS servers, spoofing the source IP address of the targeted victim. The attacker tries to request as much information as possible, thus amplifying the DNS response that is sent to the targeted victim. Since the size of the request is significantly smaller than the response, the attacker is easily able to increase the amount of traffic directed at the target. Simple Network Management Protocol (SNMP) and Network Time Protocol (NTP) can also be exploited as reflectors in an amplification attack. An example of an amplified DDoS attack through

904-508: A DoS from a web browser . Security experts quoted by the BBC indicated that well-written firewall rules can filter out most traffic from DDoS attacks by LOIC, thus preventing the attacks from being fully effective. In at least one instance, filtering out all UDP and ICMP traffic blocked a LOIC attack. Firewall rules of this sort are more likely to be effective when implemented at a point upstream of an application server's Internet uplink to avoid

1017-628: A HTTP pipelining DDoS attack on Sept. 5. 2021 that originated from unpatched Mikrotik networking gear. In the first half of 2022, the Russian invasion of Ukraine significantly shaped the cyberthreat landscape, with an increase in cyberattacks attributed to both state-sponsored actors and global hacktivist activities. The most notable event was a DDoS attack in February, the largest Ukraine has encountered, disrupting government and financial sector services. This wave of cyber aggression extended to Western allies like

1130-409: A denial-of-service attack. Exposure of degradation-of-service attacks is complicated further by the matter of discerning whether the server is really being attacked or is experiencing higher than normal legitimate traffic loads. If an attacker mounts an attack from a single host, it would be classified as a DoS attack. Any attack against availability would be classed as a denial-of-service attack. On

1243-509: A diversion to evade defensive DDoS countermeasures but all the while eventually concentrating the main thrust of the attack onto a single victim. In this scenario, attackers with continuous access to several very powerful network resources are capable of sustaining a prolonged campaign generating enormous levels of unamplified DDoS traffic. APDoS attacks are characterized by: Some vendors provide so-called booter or stresser services, which have simple web-based front ends, and accept payment over

SECTION 10

#1732868703165

1356-423: A hacking tool to send these kinds of requests to attack a NSFOCUS firewall named Collapsar, and thus the hacking tool was known as Challenge Collapsar, or CC for short. Consequently, this type of attack got the name CC attack . A smurf attack relies on misconfigured network devices that allow packets to be sent to all computer hosts on a particular network via the broadcast address of the network, rather than

1469-1060: A long time and so Apache suffered, even more, the competition of commercial servers and, above all, of other open-source servers which meanwhile had already achieved far superior performances (mostly when serving static content) since the beginning of their development and at the time of the Apache decline were able to offer also a long enough list of well tested advanced features. In fact, a few years after 2000 started, not only other commercial and highly competitive web servers, e.g. LiteSpeed , but also many other open-source programs, often of excellent quality and very high performances, among which should be noted Hiawatha , Cherokee HTTP server , Lighttpd , Nginx and other derived/related products also available with commercial support, emerged. Around 2007–2008, most popular web browsers increased their previous default limit of 2 persistent connections per host-domain (a limit recommended by RFC-2616) to 4, 6 or 8 persistent connections per host-domain, in order to speed up

1582-540: A loop of paper at the sender. It takes more router resources to drop a packet with a TTL value of 1 or less than it does to forward a packet with a higher TTL value. When a packet is dropped due to TTL expiry, the router CPU must generate and send an ICMP time exceeded response. Generating many of these responses can overload the router's CPU. A UPnP attack uses an existing vulnerability in Universal Plug and Play (UPnP) protocol to get past network security and flood

1695-459: A low-level attack and a warning that a larger attack will be carried out if a ransom is not paid in bitcoin . Security experts recommend targeted websites to not pay the ransom. The attackers tend to get into an extended extortion scheme once they recognize that the target is ready to pay. First discovered in 2009, the HTTP slow POST attack sends a complete, legitimate HTTP POST header , which includes

1808-435: A machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connected to a network . Denial of service is typically accomplished by flooding the targeted machine or resource with superfluous requests in an attempt to overload systems and prevent some or all legitimate requests from being fulfilled. The range of attacks varies widely, spanning from inundating

1921-460: A physical file system path, to an absolute path under the target website's root directory. Website's root directory may be specified by a configuration file or by some internal rule of the web server by using the name of the website which is the host part of the URL found in HTTP client request. Path translation to file system is done for the following types of web resources: The web server appends

2034-450: A piece of malware that targeted IoT devices, used PDoS attacks to disable its targets. PhlashDance is a tool created by Rich Smith (an employee of Hewlett-Packard 's Systems Security Lab) used to detect and demonstrate PDoS vulnerabilities at the 2008 EUSecWest Applied Security Conference in London, UK. A distributed denial-of-service attack may involve sending forged requests of some type to

2147-459: A record-breaking packet DDoS at 3.15 billion packets per second, which targeted an undisclosed number of unofficial Minecraft game servers . In October 2024, the Internet Archive faced two severe DDoS attacks that brought the site completely offline, immediately following a previous attack that leaked records of over 31 million of the site's users. The hacktivist group SN_Blackmeta claimed

2260-430: A server with millions of requests to slow its performance, overwhelming a server with a substantial amount of invalid data, to submitting requests with an illegitimate IP address . In a distributed denial-of-service attack ( DDoS attack ), the incoming traffic flooding the victim originates from many different sources. More sophisticated strategies are required to mitigate this type of attack; simply attempting to block

2373-479: A single machine and are harder to disable, and the behavior of each attack machine can be stealthier, making the attack harder to track and shut down. Since the incoming traffic flooding the victim originates from different sources, it may be impossible to stop the attack simply by using ingress filtering . It also makes it difficult to distinguish legitimate user traffic from attack traffic when spread across multiple points of origin. As an alternative or augmentation of

SECTION 20

#1732868703165

2486-510: A single source is insufficient as there are multiple sources. A DoS or DDoS attack is analogous to a group of people crowding the entry door of a shop, making it hard for legitimate customers to enter, thus disrupting trade and losing the business money. Criminal perpetrators of DoS attacks often target sites or services hosted on high-profile web servers such as banks or credit card payment gateways . Revenge and blackmail , as well as hacktivism , can motivate these attacks. Panix ,

2599-416: A specific machine. The attacker will send large numbers of IP packets with the source address faked to appear to be the address of the victim. Most devices on a network will, by default, respond to this by sending a reply to the source IP address. If the number of machines on the network that receive and respond to these packets is very large, the victim's computer will be flooded with traffic. This overloads

2712-428: A strong impetus to the adoption of reverse proxies in front of slower web servers and it gave also one more chance to the emerging new web servers that could show all their speed and their capability to handle very high numbers of concurrent connections without requiring too many hardware resources (expensive computers with lots of CPUs, RAM and fast disks). In 2015, RFCs published new protocol version [HTTP/2], and as

2825-430: A system crash on a vulnerable system. The BlackNurse attack is an example of an attack taking advantage of the required Destination Port Unreachable ICMP packets. A nuke is an old-fashioned denial-of-service attack against computer networks consisting of fragmented or otherwise invalid ICMP packets sent to the target, achieved by using a modified ping utility to repeatedly send this corrupt data , thus slowing down

2938-471: A target's network and servers. The attack is based on a DNS amplification technique, but the attack mechanism is a UPnP router that forwards requests from one outer source to another. The UPnP router returns the data on an unexpected UDP port from a bogus IP address, making it harder to take simple action to shut down the traffic flood. According to the Imperva researchers, the most effective way to stop this attack

3051-432: A tool to test the security of servers against this type of attack. A Challenge Collapsar (CC) attack is an attack where standard HTTP requests are sent to a targeted web server frequently. The Uniform Resource Identifiers (URIs) in the requests require complicated time-consuming algorithms or database operations which may exhaust the resources of the targeted web server. In 2004, a Chinese hacker nicknamed KiKi invented

3164-438: A very large number of computers that will reply to the requests. Using Internet Protocol address spoofing , the source address is set to that of the targeted victim, which means all the replies will go to (and flood) the target. This reflected attack form is sometimes called a distributed reflective denial-of-service ( DRDoS ) attack. ICMP echo request attacks ( Smurf attacks ) can be considered one form of reflected attack, as

3277-400: A very long time. The attacker establishes hundreds or even thousands of such connections until all resources for incoming connections on the victim server are exhausted, making any further connections impossible until all data has been sent. It is notable that unlike many other DDoS or DDoS attacks, which try to subdue the server by overloading its network or CPU, an HTTP slow POST attack targets

3390-447: A web server and some of the tasks that it may perform in order to have a sufficiently wide scenario about the topic. A web server program plays the role of a server in a client–server model by implementing one or more versions of HTTP protocol, often including the HTTPS secure variant and other features and extensions that are considered useful for its planned usage. The complexity and

3503-427: A web server implements one or more of the above-mentioned advanced features then the path part of a valid URL may not always match an existing file system path under website directory tree (a file or a directory in file system ) because it can refer to a virtual name of an internal or external module processor for dynamic requests. Web server programs are able to translate an URL path (all or part of it), that refers to

Low Orbit Ion Cannon - Misplaced Pages Continue

3616-594: A wide range of source IP addresses, giving the appearance of a distributed DoS. These flood attacks do not require completion of the TCP three-way handshake and attempt to exhaust the destination SYN queue or the server bandwidth. Because the source IP addresses can be trivially spoofed, an attack could come from a limited set of sources, or may even originate from a single host. Stack enhancements such as SYN cookies may be effective mitigation against SYN queue flooding but do not address bandwidth exhaustion. In 2022, TCP attacks were

3729-485: A wide variety of DDoS tools are available today, including paid and free versions, with different features available. There is an underground market for these in hacker-related forums and IRC channels. Application-layer attacks employ DoS-causing exploits and can cause server-running software to fill the disk space or consume all available memory or CPU time . Attacks may use specific packet types or connection requests to saturate finite resources by, for example, occupying

3842-543: Is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers . The model is a product of the Open Systems Interconnection project at the International Organization for Standardization (ISO). The model groups similar communication functions into one of seven logical layers. A layer serves the layer above it and

3955-503: Is a denial-of-service attack on the Transmission Control Protocol where the attacker employs man-in-the-middle techniques . It exploits a weakness in TCP's re-transmission timeout mechanism, using short synchronized bursts of traffic to disrupt TCP connections on the same link. A slow read attack sends legitimate application layer requests, but reads responses very slowly, keeping connections open longer hoping to exhaust

4068-1047: Is a form of DDoS attack where attackers target application-layer processes. The attack over-exercises specific functions or features of a website with the intention to disable those functions or features. This application-layer attack is different from an entire network attack, and is often used against financial institutions to distract IT and security personnel from security breaches. In 2013, application-layer DDoS attacks represented 20% of all DDoS attacks. According to research by Akamai Technologies , there have been "51 percent more application layer attacks" from Q4 2013 to Q4 2014 and "16 percent more" from Q3 2014 to Q4 2014. In November 2017; Junade Ali, an engineer at Cloudflare noted that whilst network-level attacks continue to be of high capacity, they were occurring less frequently. Ali further noted that although network-level attacks were becoming less frequent, data from Cloudflare demonstrated that application-layer attacks were still showing no sign of slowing down. The OSI model (ISO/IEC 7498-1)

4181-508: Is for companies to lock down UPnP routers. In 2014, it was discovered that Simple Service Discovery Protocol (SSDP) was being used in DDoS attacks known as an SSDP reflection attac k with amplification . Many devices, including some residential routers, have a vulnerability in the UPnP software that allows an attacker to get replies from UDP port 1900 to a destination address of their choice. With

4294-402: Is handled like a connection request, causing the server to spawn a half-open connection , send back a TCP/SYN-ACK packet, and wait for a packet in response from the sender address. However, because the sender's address is forged, the response never comes. These half-open connections exhaust the available connections the server can make, keeping it from responding to legitimate requests until after

4407-480: Is no botnet and the attacker does not have to communicate with the clients it subverts. Instead, the attacker acts as a puppet master , instructing clients of large peer-to-peer file sharing hubs to disconnect from their peer-to-peer network and to connect to the victim's website instead. Permanent denial-of-service (PDoS), also known loosely as phlashing, is an attack that damages a system so badly that it requires replacement or reinstallation of hardware. Unlike

4520-481: Is referring to, so that that resource can be returned to the requesting client. This process is performed with every request that is made to a web server, with some of the requests being served with a file, such as an HTML document, or a gif image, others with the results of running a CGI program, and others by some other process, such as a built-in module handler, a PHP document, or a Java servlet." In practice, web server programs that implement advanced features, beyond

4633-470: Is served by the layer below it. For example, a layer that provides error-free communications across a network provides the communications path needed by applications above it, while it calls the next lower layer to send and receive packets that traverse that path. In the OSI model, the definition of its application layer is narrower in scope than is often implemented. The OSI model defines the application layer as being

Low Orbit Ion Cannon - Misplaced Pages Continue

4746-457: Is to brick the device, rendering it unusable for its original purpose until it can be repaired or replaced. The PDoS is a pure hardware-targeted attack that can be much faster and requires fewer resources than using a botnet in a DDoS attack. Because of these features, and the potential and high probability of security exploits on network-enabled embedded devices, this technique has come to the attention of numerous hacking communities. BrickerBot ,

4859-488: Is unlikely to meet the $ 30,000 Bitcoin ransom. In August 2023, the group of hacktivists NoName057 targeted several Italian financial institutions, through the execution of slow DoS attacks . On 14 January 2024, they executed a DDoS attack on Swiss federal websites, prompted by President Zelensky 's attendance at the Davos World Economic Forum . Switzerland's National Cyber Security Centre quickly mitigated

4972-402: The 2002 New Hampshire Senate election phone jamming scandal , telemarketers were used to flood political opponents with spurious calls to jam phone banks on election day. Widespread publication of a number can also flood it with enough calls to render it unusable, as happened by accident in 1981 with multiple +1- area code -867-5309 subscribers inundated by hundreds of calls daily in response to

5085-598: The CGI to communicate with external programs. These capabilities, along with the multimedia features of NCSA's Mosaic browser (also able to manage HTML FORMs in order to send data to a web server) highlighted the potential of web technology for publishing and distributed computing applications. In the second half of 1994, the development of NCSA httpd stalled to the point that a group of external software developers, webmasters and other professional figures interested in that server, started to write and collect patches thanks to

5198-508: The Las Vegas Strip for over an hour. The release of sample code during the event led to the online attack of Sprint , EarthLink , E-Trade , and other major corporations in the year to follow. The largest DDoS attack to date happened in September 2017, when Google Cloud experienced an attack with a peak volume of 2.54 Tb/s , revealed by Google on October 17, 2020. The record holder

5311-739: The United States Department of Justice , the United States Copyright Office , the Federal Bureau of Investigation , the MPAA , Warner Music Group and the RIAA , as well as the HADOPI , all on the afternoon of January 19, 2012, through LOIC. In general, the attack hoped to retaliate against those who Anonymous members believed harmed their digital freedoms. The LOIC application is named after

5424-446: The bandwidth or resources of a targeted system, usually one or more web servers. A DDoS attack uses more than one unique IP address or machines, often from thousands of hosts infected with malware . A distributed denial of service attack typically involves more than around 3–5 nodes on different networks; fewer nodes may qualify as a DoS attack but is not a DDoS attack. Multiple attack machines can generate more attack traffic than

5537-463: The ion cannon , a fictional weapon from many sci-fi works, video games, and in particular after its namesake from the Command & Conquer series. The artwork used in the application was a concept art for Command & Conquer 3: Tiberium Wars . Denial-of-service attacks In computing , a denial-of-service attack ( DoS attack ) is a cyber-attack in which the perpetrator seeks to make

5650-554: The logical resources of the victim, which means the victim would still have enough network bandwidth and processing power to operate. Combined with the fact that the Apache HTTP Server will, by default, accept requests up to 2GB in size, this attack can be particularly powerful. HTTP slow POST attacks are difficult to differentiate from legitimate connections and are therefore able to bypass some protection systems. OWASP , an open source web application security project, released

5763-475: The public domain . This statement freed web server developers from any possible legal issue about the development of derivative work based on that source code (a threat that in practice never existed). At the beginning of 1994, the most notable among new web servers was NCSA httpd which ran on a variety of Unix -based OSs and could serve dynamically generated content by implementing the POST HTTP method and

SECTION 50

#1732868703165

5876-797: The DDoS attack as retribution for American involvement in the Israel–Hamas war , despite the Internet Archive being unaffiliated with the United States government; however, their link with the preceding data leak remains unclear. Denial-of-service attacks are characterized by an explicit attempt by attackers to prevent legitimate use of a service. There are two general forms of DoS attacks: those that crash services and those that flood services. The most serious attacks are distributed. A distributed denial-of-service (DDoS) attack occurs when multiple systems flood

5989-619: The NCSA httpd source code being available to the public domain. At the beginning of 1995 those patches were all applied to the last release of NCSA source code and, after several tests, the Apache HTTP server project was started. At the end of 1994, a new commercial web server, named Netsite , was released with specific features. It was the first one of many other similar products that were developed first by Netscape , then also by Sun Microsystems , and finally by Oracle Corporation . In mid-1995,

6102-466: The NTP is through a command called monlist, which sends the details of the last 600 hosts that have requested the time from the NTP server back to the requester. A small request to this time server can be sent using a spoofed source IP address of some victim, which results in a response 556.9 times the size of the request being sent to the victim. This becomes amplified when using botnets that all send requests with

6215-549: The UK, the US, and Germany. Particularly, the UK's financial sector saw an increase in DDoS attacks from nation-state actors and hacktivists, aimed at undermining Ukraine's allies. In February 2023, Cloudflare faced a 71 million/requests per second attack which Cloudflare claims was the largest HTTP DDoS attack at the time. HTTP DDoS attacks are measured by HTTP requests per second instead of packets per second or bits per second. On July 10, 2023,

6328-441: The above-mentioned history articles. In March 1989, Sir Tim Berners-Lee proposed a new project to his employer CERN , with the goal of easing the exchange of information between scientists by using a hypertext system. The proposal titled "HyperText and CERN" , asked for comments and it was read by several people. In October 1990 the proposal was reformulated and enriched (having as co-author Robert Cailliau ), and finally, it

6441-399: The adoption and the usage of those programs along with their porting to other operating systems . In December 1991, the first web server outside Europe was installed at SLAC (U.S.A.). This was a very important event because it started trans-continental web communications between web browsers and web servers. In 1991–1993, CERN web server program continued to be actively developed by

6554-709: The affected computer until it comes to a complete stop. A specific example of a nuke attack that gained some prominence is the WinNuke , which exploited the vulnerability in the NetBIOS handler in Windows 95 . A string of out-of-band data was sent to TCP port 139 of the victim's machine, causing it to lock up and display a Blue Screen of Death . Attackers have found a way to exploit a number of bugs in peer-to-peer servers to initiate DDoS attacks. The most aggressive of these peer-to-peer-DDoS attacks exploits DC++ . With peer-to-peer there

6667-518: The application layer can disrupt services such as the retrieval of information or search functions on a website. An advanced persistent DoS (APDoS) is associated with an advanced persistent threat and requires specialized DDoS mitigation . These attacks can persist for weeks; the longest continuous period noted so far lasted 38 days. This attack involved approximately 50+ petabits (50,000+ terabits) of malicious traffic. Attackers in this scenario may tactically switch between several targets to create

6780-542: The application of web servers well beyond their original purpose of serving human-readable pages. This is a very brief history of web server programs , so some information necessarily overlaps with the histories of the web browsers , the World Wide Web and the Internet ; therefore, for the sake of clarity and understandability, some key historical information below reported may be similar to that found also in one or more of

6893-423: The attack ends. A teardrop attack involves sending mangled IP fragments with overlapping, oversized payloads to the target machine. This can crash various operating systems because of a bug in their TCP/IP fragmentation re-assembly code. Windows 3.1x , Windows 95 and Windows NT operating systems, as well as versions of Linux prior to versions 2.0.32 and 2.1.63 are vulnerable to this attack. One of

SECTION 60

#1732868703165

7006-531: The attack, ensuring core federal services remained secure, despite temporary accessibility issues on some websites. In October 2023, exploitation of a new vulnerability in the HTTP/2 protocol resulted in the record for largest HTTP DDoS attack being broken twice, once with a 201 million requests per second attack observed by Cloudflare, and again with a 398 million requests per second attack observed by Google . In August 2024, Global Secure Layer observed and reported on

7119-411: The attacker disrupts control packets using a hidden Markov model . A setting in which Markov-model based attacks are prevalent is online gaming as the disruption of the control packet undermines game play and system functionality. The United States Computer Emergency Readiness Team (US-CERT) has identified symptoms of a denial-of-service attack to include: In cases such as MyDoom and Slowloris ,

7232-440: The attacker sends traffic consisting of complicated requests to the system. Essentially, a sophisticated DDoS attack is lower in cost due to its use of less traffic, is smaller in size making it more difficult to identify, and it has the ability to hurt systems which are protected by flow control mechanisms. A SYN flood occurs when a host sends a flood of TCP/SYN packets, often with a forged sender address. Each of these packets

7345-474: The attacker uses a client program to connect to handlers, which are compromised systems that issue commands to the zombie agents, which in turn facilitate the DDoS attack. Agents are compromised via the handlers by the attacker. Each handler can control up to a thousand agents. In some cases a machine may become part of a DDoS attack with the owner's consent, for example, in Operation Payback , organized by

7458-452: The attacker using automated routines to exploit vulnerabilities in programs that accept remote connections running on the targeted remote hosts. Each handler can control up to a thousand agents. In other cases a machine may become part of a DDoS attack with the owner's consent, for example, in Operation Payback organized by the group Anonymous . The Low Orbit Ion Cannon has typically been used in this way. Along with High Orbit Ion Cannon

7571-537: The availability of new protocol , not only because they had the work force and the time to do so, but also because usually their previous implementation of SPDY protocol could be reused as a starting point and because most used web browsers implemented it very quickly for the same reason. Another reason that prompted those developers to act quickly was that webmasters felt the pressure of the ever increasing web traffic and they really wanted to install and to try – as soon as possible – something that could drastically lower

7684-592: The availability of well known websites to legitimate users. More sophisticated attackers use DDoS tools for the purposes of extortion  – including against their business rivals. It has been reported that there are new attacks from internet of things (IoT) devices that have been involved in denial of service attacks. In one noted attack that was made peaked at around 20,000 requests per second which came from around 900 CCTV cameras. UK's GCHQ has tools built for DDoS, named PREDATORS FACE and ROLLING THUNDER. Simple attacks such as SYN floods may appear with

7797-541: The client, preventing outside access, as well as flooding the client with the sent packets. A LAND attack is of this type. Pulsing zombies are compromised computers that are directed to launch intermittent and short-lived floodings of victim websites with the intent of merely slowing it rather than crashing it. This type of attack, referred to as degradation-of-service , can be more difficult to detect and can disrupt and hamper connection to websites for prolonged periods of time, potentially causing more overall disruption than

7910-559: The device becomes infected. The IoT device itself is not the direct target of the attack, it is used as a part of a larger attack. Once the hacker has enslaved the desired number of devices, they instruct the devices to try to contact an ISP. In October 2016, a Mirai botnet attacked Dyn which is the ISP for sites such as Twitter , Netflix , etc. As soon as this occurred, these websites were all unreachable for several hours. RUDY attack targets web applications by starvation of available sessions on

8023-432: The distributed denial-of-service attack, a PDoS attack exploits security flaws which allow remote administration on the management interfaces of the victim's hardware, such as routers , printers, or other networking hardware . The attacker uses these vulnerabilities to replace a device's firmware with a modified, corrupt, or defective firmware image—a process which when done legitimately is known as flashing. The intent

8136-870: The efficiency of a web server program may vary a lot depending on (e.g.): Although web server programs differ in how they are implemented, most of them offer the following common features. These are basic features that most web servers usually have. A few other more advanced and popular features ( only a very short selection ) are the following ones. A web server program, when it is running, usually performs several general tasks , (e.g.): Web server programs are able: Once an HTTP request message has been decoded and verified, its values can be used to determine whether that request can be satisfied or not. This requires many other steps, including security checks . Web server programs usually perform some type of URL normalization ( URL found in most HTTP request messages) in order to: The term URL normalization refers to

8249-425: The fanfiction platform Archive of Our Own (AO3) faced DDoS attacks, disrupting services. Anonymous Sudan , claiming the attack for religious and political reasons, was viewed skeptically by AO3 and experts. Flashpoint, a threat intelligence vendor, noted the group's past activities but doubted their stated motives. AO3, supported by the non-profit Organization for Transformative Works (OTW) and reliant on donations,

8362-407: The fields in an IP header is the fragment offset field, indicating the starting position, or offset, of the data contained in a fragmented packet relative to the data in the original packet. If the sum of the offset and size of one fragmented packet differs from that of the next fragmented packet, the packets overlap. When this happens, a server vulnerable to teardrop attacks is unable to reassemble

8475-406: The first version of IIS was released, for Windows NT OS, by Microsoft . This marked the entry, in the field of World Wide Web technologies, of a very important commercial developer and vendor that has played and still is playing a key role on both sides (client and server) of the web. In the second half of 1995, CERN and NCSA web servers started to decline (in global percentage usage) because of

8588-574: The flooding hosts send Echo Requests to the broadcast addresses of mis-configured networks, thereby enticing hosts to send Echo Reply packets to the victim. Some early DDoS programs implemented a distributed form of this attack. Amplification attacks are used to magnify the bandwidth that is sent to a victim. Many services can be exploited to act as reflectors, some harder to block than others. US-CERT have observed that different services may result in different amplification factors, as tabulated below: DNS amplification attacks involves an attacker sending

8701-597: The group Anonymous . These attacks can use different types of internet packets such as TCP, UDP, ICMP, etc. These collections of compromised systems are known as botnets . DDoS tools like Stacheldraht still use classic DoS attack methods centered on IP spoofing and amplification like smurf attacks and fraggle attacks (types of bandwidth consumption attacks). SYN floods (a resource starvation attack) may also be used. Newer tools can use DNS servers for DoS purposes. Unlike MyDoom's DDoS mechanism, botnets can be turned against any IP address. Script kiddies use them to deny

8814-483: The implementation of new specifications was not trivial at all, a dilemma arose among developers of less popular web servers (e.g. with a percentage of usage lower than 1% .. 2%), about adding or not adding support for that new protocol version. In fact supporting HTTP/2 often required radical changes to their internal implementation due to many factors (practically always required encrypted connections, capability to distinguish between HTTP/1.x and HTTP/2 connections on

8927-407: The leading method in DDoS incidents, accounting for 63% of all DDoS activity. This includes tactics like TCP SYN , TCP ACK, and TCP floods. With TCP being the most widespread networking protocol, its attacks are expected to remain prevalent in the DDoS threat scene. In 2015, DDoS botnets such as DD4BC grew in prominence, taking aim at financial institutions. Cyber-extortionists typically begin with

9040-405: The low end of the range are embedded systems , such as a router that runs a small web server as its configuration interface. A high-traffic Internet website might handle requests with hundreds of servers that run on racks of high-speed computers. A resource sent from a web server can be a pre-existing file ( static content ) available to the web server, or it can be generated at the time of

9153-408: The maximum number of concurrent connections allowed and to improve their level of scalability. Between 1996 and 1999, Netscape Enterprise Server and Microsoft's IIS emerged among the leading commercial options whereas among the freely available and open-source programs Apache HTTP Server held the lead as the preferred server (because of its reliability and its many features). In those years there

9266-545: The maximum number of open connections or filling the victim's disk space with logs. An attacker with shell-level access to a victim's computer may slow it until it is unusable or crash it by using a fork bomb . Another kind of application-level DoS attack is XDoS (or XML DoS) which can be controlled by modern web application firewalls (WAFs). All attacks belonging to the category of timeout exploiting . Slow DoS attacks implement an application-layer attack. Examples of threats are Slowloris, establishing pending connections with

9379-496: The number of TCP/IP connections and speedup accesses to hosted websites. In 2020–2021 the HTTP/2 dynamics about its implementation (by top web servers and popular web browsers) were partly replicated after the publication of advanced drafts of future RFC about HTTP/3 protocol. The following technical overview should be considered only as an attempt to give a few very limited examples about some features that may be implemented in

9492-425: The other hand, if an attacker uses many systems to simultaneously launch attacks against a remote host, this would be classified as a DDoS attack. Malware can carry DDoS attack mechanisms; one of the better-known examples of this was MyDoom . Its DoS mechanism was triggered on a specific date and time. This type of DDoS involved hardcoding the target IP address before releasing the malware and no further interaction

9605-518: The packets resulting in a denial-of-service condition. Voice over IP has made abusive origination of large numbers of telephone voice calls inexpensive and easily automated while permitting call origins to be misrepresented through caller ID spoofing . According to the US Federal Bureau of Investigation , telephony denial-of-service (TDoS) has appeared as part of various fraudulent schemes: TDoS can exist even without Internet telephony . In

9718-431: The process of modifying and standardizing a URL in a consistent manner. There are several types of normalization that may be performed, including the conversion of the scheme and host to lowercase. Among the most important normalizations are the removal of "." and ".." path segments and adding trailing slashes to a non-empty path component. "URL mapping is the process by which a URL is analyzed to figure out what resource it

9831-414: The provider to meet the defined QoS levels for the increased requests. The main incentive behind such attacks may be to drive the application owner to raise the elasticity levels to handle the increased application traffic, to cause financial losses, or force them to become less competitive. A banana attack is another particular type of DoS. It involves redirecting outgoing messages from the client back onto

9944-424: The request ( dynamic content ) by another program that communicates with the server software. The former usually can be served faster and can be more easily cached for repeated requests, while the latter supports a broader range of applications. Technologies such as REST and SOAP , which use HTTP as a basis for general computer-to-computer communication, as well as support for WebDAV extensions, have extended

10057-429: The retrieval of heavy web pages with lots of images, and to mitigate the problem of the shortage of persistent connections dedicated to dynamic objects used for bi-directional notifications of events in web pages. Within a year, these changes, on average, nearly tripled the maximum number of persistent connections that web servers had to manage. This trend (of increasing the number of persistent connections) definitely gave

10170-416: The same TCP port, binary representation of HTTP messages, message priority, compression of HTTP headers, use of streams also known as TCP/IP sub-connections and related flow-control, etc.) and so a few developers of those web servers opted for not supporting new HTTP/2 version (at least in the near future) also because of these main reasons: Instead, developers of most popular web servers, rushed to offer

10283-403: The same spoofed IP source, which will result in a massive amount of data being sent back to the victim. It is very difficult to defend against these types of attacks because the response data is coming from legitimate servers. These attack requests are also sent through UDP, which does not require a connection to the server. This means that the source IP is not verified when a request is received by

10396-470: The server's connection pool. The slow read is achieved by advertising a very small number for the TCP Receive Window size, and at the same time emptying clients' TCP receive buffer slowly, which causes a very low data flow rate. A sophisticated low-bandwidth DDoS attack is a form of DoS that uses less traffic and increases its effectiveness by aiming at a weak point in the victim's system design, i.e.,

10509-583: The server. To bring awareness of these vulnerabilities, campaigns have been started that are dedicated to finding amplification vectors which have led to people fixing their resolvers or having the resolvers shut down completely. The Mirai botnet works by using a computer worm to infect hundreds of thousands of IoT devices across the internet. The worm propagates through networks and systems taking control of poorly protected IoT devices such as thermostats, Wi-Fi-enabled clocks, and washing machines. The owner or user will usually have no immediate indication of when

10622-426: The simple static content serving (e.g. URL rewrite engine, dynamic content serving), usually have to figure out how that URL has to be handled, e.g. as a: One or more configuration files of web server may specify the mapping of parts of URL path (e.g. initial parts of file path , filename extension and other path components) to a specific URL handler (file, directory, external program or internal module). When

10735-418: The song " 867-5309/Jenny ". TDoS differs from other telephone harassment (such as prank calls and obscene phone calls ) by the number of calls originated. By occupying lines continuously with repeated automated calls, the victim is prevented from making or receiving both routine and emergency telephone calls. Related exploits include SMS flooding attacks and black fax or continuous fax transmission by using

10848-590: The target's system resources. Bandwidth-saturating floods rely on the attacker's ability to generate the overwhelming flux of packets. A common way of achieving this today is via distributed denial-of-service, employing a botnet . An application layer DDoS attack is done mainly for specific targeted purposes, including disrupting transactions and access to databases. It requires fewer resources than network layer attacks but often accompanies them. An attack may be disguised to look like legitimate traffic, except it targets specific application packets or functions. The attack on

10961-466: The third-oldest ISP in the world, was the target of what is thought to be the first DoS attack. On September 6, 1996, Panix was subject to a SYN flood attack, which brought down its services for several days while hardware vendors, notably Cisco , figured out a proper defense. Another early demonstration of the DoS attack was made by Khan C. Smith in 1997 during a DEF CON event, disrupting Internet access to

11074-407: The tools are embedded in malware and launch their attacks without the knowledge of the system owner. Stacheldraht is a classic example of a DDoS tool. It uses a layered structure where the attacker uses a client program to connect to handlers which are compromised systems that issue commands to the zombie agents which in turn facilitate the DDoS attack. Agents are compromised via the handlers by

11187-650: The uplink from exceeding its capacity. LOIC attacks are easily identified in system logs, and the attack can be tracked down to the IP addresses used. LOIC was used by Anonymous (a group that spawned from the /b/ board of 4chan ) during Project Chanology to attack websites from the Church of Scientology , once more to (successfully) attack the Recording Industry Association of America 's website in October 2010, and it

11300-448: The user interface. The OSI application layer is responsible for displaying data and images to the user in a human-recognizable format and to interface with the presentation layer below it. In an implementation, the application and presentation layers are frequently combined. The simplest DoS attack relies primarily on brute force, flooding the target with an overwhelming flux of packets, oversaturating its connection bandwidth or depleting

11413-499: The victim scales back down, the attack resumes, causing resources to scale back up again. This can result in a reduced quality of service during the periods of scaling up and down and a financial drain on resources during periods of over-provisioning while operating with a lower cost for an attacker compared to a normal DDoS attack, as it only needs to be generating traffic for a portion of the attack period. An application layer DDoS attack (sometimes referred to as layer 7 DDoS attack )

11526-418: The victim's computer and can even make it unusable during such an attack. Ping flood is based on sending the victim an overwhelming number of ping packets, usually using the ping command from Unix-like hosts. It is very simple to launch, the primary requirement being access to greater bandwidth than the victim. Ping of death is based on sending the victim a malformed ping packet, which will lead to

11639-482: The victim, or SlowDroid , an attack running on mobile devices. Another target of DDoS attacks may be to produce added costs for the application operator, when the latter uses resources based on cloud computing . In this case, normally application-used resources are tied to a needed quality of service (QoS) level (e.g. responses should be less than 200 ms) and this rule is usually linked to automated software (e.g. Amazon CloudWatch ) to raise more virtual resources from

11752-562: The web server. Much like Slowloris, RUDY keeps sessions at halt using never-ending POST transmissions and sending an arbitrarily large content-length header value. Manipulating maximum segment size and selective acknowledgement (SACK) may be used by a remote peer to cause a denial of service by an integer overflow in the Linux kernel, potentially causing a kernel panic . Jonathan Looney discovered CVE - 2019-11477 , CVE- 2019-11478 , CVE- 2019-11479 on June 17, 2019. The shrew attack

11865-454: The web. Marketed and promoted as stress-testing tools, they can be used to perform unauthorized denial-of-service attacks, and allow technically unsophisticated attackers access to sophisticated attack tools. Usually powered by a botnet, the traffic produced by a consumer stresser can range anywhere from 5-50 Gbit/s, which can, in most cases, deny the average home user internet access. A Markov-modulated denial-of-service attack occurs when

11978-720: The widespread adoption of new web servers which had a much faster development cycle along with more features, more fixes applied, and more performances than the previous ones. At the end of 1996, there were already over fifty known (different) web server software programs that were available to everybody who wanted to own an Internet domain name and/or to host websites. Many of them lived only shortly and were replaced by other web servers. The publication of RFCs about protocol versions HTTP/1.0 (1996) and HTTP/1.1 (1997, 1999), forced most web servers to comply (not always completely) with those standards. The use of TCP/IP persistent connections (HTTP/1.1) required web servers both to increase

12091-418: The www group, meanwhile, thanks to the availability of its source code and the public specifications of the HTTP protocol, many other implementations of web servers started to be developed. In April 1993, CERN issued a public official statement stating that the three components of Web software (the basic line-mode client, the web server and the library of common code), along with their source code , were put in

12204-468: Was again used by Anonymous during their Operation Payback in December 2010 to attack the websites of companies and organizations that opposed WikiLeaks . In retaliation for the shutdown of the file sharing service Megaupload and the arrest of four workers, members of Anonymous launched a DDoS attack upon the websites of Universal Music Group (the company responsible for the lawsuit against Megaupload),

12317-817: Was also another commercial, highly innovative and thus notable web server called Zeus ( now discontinued ) that was known as one of the fastest and most scalable web servers available on market, at least till the first decade of 2000s, despite its low percentage of usage. Apache resulted in the most used web server from mid-1996 to the end of 2015 when, after a few years of decline, it was surpassed initially by IIS and then by Nginx. Afterward IIS dropped to much lower percentages of usage than Apache (see also market share ). From 2005–2006, Apache started to improve its speed and its scalability level by introducing new performance features (e.g. event MPM and new content cache). As those new performance improvements initially were marked as experimental, they were not enabled by its users for

12430-455: Was approved. Between late 1990 and early 1991 the project resulted in Berners-Lee and his developers writing and testing several software libraries along with three programs, which initially ran on NeXTSTEP OS installed on NeXT workstations: Those early browsers retrieved web pages written in a simple early form of HTML , from web server(s) using a new basic communication protocol that

12543-472: Was named HTTP 0.9 . In August 1991 Tim Berners-Lee announced the birth of WWW technology and encouraged scientists to adopt and develop it. Soon after, those programs, along with their source code , were made available to people interested in their usage. Although the source code was not formally licensed or placed in the public domain, CERN informally allowed users and developers to experiment and further develop on top of them. Berners-Lee started promoting

12656-408: Was necessary to launch the attack. A system may also be compromised with a trojan containing a zombie agent . Attackers can also break into systems using automated tools that exploit flaws in programs that listen for connections from remote hosts. This scenario primarily concerns systems acting as servers on the web. Stacheldraht is a classic example of a DDoS tool. It uses a layered structure where

12769-537: Was thought to be an attack executed by an unnamed customer of the US-based service provider Arbor Networks , reaching a peak of about 1.7 Tb/s . In February 2020, Amazon Web Services experienced an attack with a peak volume of 2.3 Tb/s . In July 2021, CDN Provider Cloudflare boasted of protecting its client from a DDoS attack from a global Mirai botnet that was up to 17.2 million requests per second. Russian DDoS prevention provider Yandex said it blocked

#164835